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163 Cards in this Set
- Front
- Back
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What is a tropic hormone?
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a hormone that controls other endocrine tissues to ultimately affect production or secretion of another hormone.
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What is a non-tropic hormone?
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A hormone that targets non-endocrine tissues and exerts effect other than hormone production/secretion
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What is a trophic hormone?
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A hormone that acts upon non-endocrine organs and tissues for the purposes of promoting cellular growth, differentiation, and survival.
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What must precede hormone degradation? Where does it take place, and how is the resulting metabolite released from the body?
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Hormone action (hormones that get "used") MUST precede degradation, by definition. The target cell degrades the hormone and the metabolite is secreted by the kidney. Inactivation is destruction of unused hormone.
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What is the process of destruction, metabolism, or removal from the body hormone that has not been used by a target cell?
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Inactivation.
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Where does inactivation of hormone take place and what happens to the resulting metabolite?
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Takes place in the liver. The metabolite is either excreted in bile or returned to plasma for excretion in the urine.
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Can peptide hormones be stored? If so, where? If not, why?
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Yes. They are water soluble and are therefore stored in storage/secretory vesicles/granules within the cell of origin.
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Comment on the speed of the onset of action of protein/peptide hormones.
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Very rapid. Since protein/peptide bind extracellularly and activate second-messengers, preexisting proenzymes are rapidly activated by a signal amplification and/or cascade.
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Can steroid hormones be stored? If so, where? If not, why?
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No, Because they are lipid soluble, they free pass through cell membranes and diffuse out of the originating cell.
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Long loop negative feedback.
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signal originates at the target gland and acts upon the hypothalamus and/or pituitary gland
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short loop negative feedback
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signal originates at the pituitary gland and acts upon the hypothalamus
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ultra-short loop negative feedback
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signal originates at the hypothalamus and acts upon the hypothalamus.
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what type of tissue is the infundibular stalk of the pituitary gland made from?
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neural tissue as a ventral extension from the median eminence of the hypothalamus
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true or false: the hypothalamus extends ventrally into and forms the pituitary gland?
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False. The ventral extension of the hypothalamus forms the stalk and pars nervosa (neurohypophysis) of the pituitary gland only. The pars intermedia. pars distalis, and pars tuberalis are derived from embryonic oral surface tissue.
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What is the role of the hypothalamus with regards to the adenohypophysis?
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Controls the function of the secretion of hormones from this part of the pituitary via the secretion of "factors" or releasing/inhibiting hormones.
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What parts of the pituitary are derived from the infundibulum of the embryo?
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- part of the infundibular stalk
- all of the neurohypophysis (posterior pituitary gland) |
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what is the vascular supply of the adenohypophysis?
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the hypophyseal portal system
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where does the hypophyseal portal system receive its blood?
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from capillary beds of the infundibular stalk of the pituitary gland that originated by an artery at the median eminance of the hypothalamus
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what is the target for hypothalamic hormones related to the posterior pituitary?
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they are released into the systemic circulation at the pituitary gland and target non-endocrine cells in the peripheral body
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what is the target for hypothalamic hormones related to the anterior pituitary?
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they are released into the pituitary circulation and act as tropic hormones that target the cells of the anterior pituitary gland.
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what is the overall function of the posterior pituitary gland? What hormones are involved?
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It does not produce its own hormones; rather, it stores those made by the hypothalamus and releases them when needed. The two hormones of the posterior pituitary gland (neurohypophysis) are oxytocin and vasopressin/ADH/AVP
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what hormone is involved in diabetes insipidus and how is it involved?
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Either the posterior pituitary gland is not secreting ADH (vasopressin) or the renal tubules are not responding to it.
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what is the basic pathway of positive feedback oxytocin release during parturition.
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stimulation of the cervical stretch receptors stimulate the brain to secrete oxytocin. Oxytocin causes contraction of the uterus, stretching the cervix, which causes stimulation of the stretch receptors and the cycle continues until the neonate is born, thus releasing stimulus of the stretch receptors and stopping oxytocin release. whew! I'm glad I'm a male.
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true or false: the anterior pituitary gland is stimulated by, makes, and releases hormones.
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true. it is stimulated by inhibiting and releasing hormones/factors from the hypothalamus and also by negative feedback from the periphery.
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how does the anterior pituitary affect lactation and what hormone is involved?
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stimulates the mammary glands to produce milk (not let-down or release) via the hormone prolactin (PRL)
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where is somatotropin produced and what does it do?
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also called Growth Hormone (GH), produced by the anterior pituitary gland and stimulates the liver to produce somatomedins (or IGFs). GH does not directly promote growth.
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where is somatostatin produced and what does it do?
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also called Growth Hormone Inhibiting Hormone (GHIH), it is produced by the hypothalamus to inhibit the anterior pituitary from producing somatotropin (aka Growth Hormone)
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where is somatomedin produced and what does it do?
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also called Insulin-like Growth Factor (IGF)--actually there is more than one of them--they are produced mainly in the liver by the stimulaton of somatotropin (Growth hormone) and promote growth of a wide variety of body tissues.
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systemic circulation of somatomedin (IGF) causes the hypothalamus to reduce the production of what and increase the production of what?
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reduces the production of Growth Hormone Releasing Hormone (GHRH) and increases the production of somatostatin (GHIH)
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systemic circulation of somatotropin (GH) causes the anterior pituitary to reduce the production of what? What does it reduce the production of in the hypothalamus? What does it increase the production of in the hypothalamus?
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anterior pituitary: reduces somatotropin (GH) production
hypothalamus: reduces Growth Hormone Releasing Hormone (GHRH) production hypothalamus: increases somatostatin (GHIH) production |
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How does IGF-1 (somatomedin) production in the liver directly affect the anterior pituitary? indirectly?
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Directly: inhibits somatotropin (GH) production
Indirectly: hypothalamus produces somatostatin (GHIH) that inhibits somatotropin production in the pituitary. The hypothalamus also decreases the production of Growth Hormone Releasing Hormone (GHRH), which removes stimulus from the pituitary to make somatotropin. |
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true or false: prolaction promotes milk let-down
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false
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true or false: oxytocin promotes milk let-down and milk production
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false; only milk let-down.
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true or false: oxytocin is the main hormone involved in uterine contraction during labor
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true
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why can skin darkening occur in patients with high ACTH levels?
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because ACTH contains, within its sequence, the exact amino acid structure of melanocyte-stimulating hormone (MSH)
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what are the two main substances required for thyroid hormone to be produced?
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iodine and tyrosine
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from what is T3 produced?
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MIT + DIT
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from what is T4 produced?
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DIT + DIT
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true or false:
triiodothyronine and tetraiodothyronine are abbreviated ***-1 and ***-2 respectively |
false: they are T3 and T4
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what tissues produce the most T3 from T4 in the body?
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liver, kidney, skeletal muscle
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what two organs, per unit weight, can convert the most grams of T4 to T3?
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liver and kidney. Note that sketal muscle does not have as much enzyme, but produces a lot of T3 because the body has so much of it.
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which thyroid hormone has the highest relative binding affinity to carrier proteins?
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T4
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which thyroid hormone has the highest relative biological activity?
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T3 (in part because it as a lower binding affinity to carrier proteins)
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what are the four cell types of the pancreatic islets and what do they produce?
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1. alpha - glucagon
2. beta - insulin 3. delta - somatostatin 4. F - pancreatic polypeptide |
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what is the function of pancreatic polypeptide and where is it produced?
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- promotes intra-islet homeostasis, affecting the production of pancreatic enzymes
- extrapancreatically related to the GI tract produced in the F-cells of the pancreatic islets |
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true or false: when insulin is secreted, glucagon production stops and vice versa. Explain your answer.
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False. They are both secreted simultaneously to keep blood glucose in a normal range. The ratio of the two hormones is what is important.
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What are the two major physiological effects of insulin secretion
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1. increase cellular permeability in almost all bodily cells
2. Stimulate energy storage in the liver, adipose tissue and resting skeletal muscle |
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What tissues are not affected by insulin?
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red and white blood cells, WORKING muscle, brain
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what is the primary stimulus for insulin secretion?
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high blood glucose
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true or false: insulin secretion and blood glucose can be considered a positive feedback mechanism?
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true. As long as there is high blood glucose, insulin will be secreted.
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besides glucose, what other stimuli cause insulin secretion?
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- hormones from the GI tract that indicate food intake
- high blood levels of protein and fatty acids - neural input suggesting food (minor) |
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what four stimuli are the major factors for reduced insulin secretion?
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1. reduction of blood glucose to normal limits.
2. reduction of fat and amino acids in the blood 3. sympathetic stimulation (bear attack = MORE GLUCOSE) 4. *****PANCREATIC SOMATOSTATIN***** |
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insulin promotes the metabolism of which macronutrients?
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fat, protein, and carbohydrates (all of them!)
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where is the major site of action of glucagon
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****LIVER****
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what is the primary stimulus of glucagon secretion?
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low blood glucose
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besides the affect of glucose, what other things affect insulin secretion?
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sympathetic and/or parasympathetic stimulation
high amino acids in the blood |
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why is glucagon released along with insulin with high blood amino acid concentrations?
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to stimulate gluconeogenesis. If the meal contained only protein, then the insulin would drop glucose to low levels, causing hypoglycemia
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there are two types of diabetes mellitus. How does each type relate to insulin?
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Type 1: beta-cells don't produce insulin
Type 2: body cells don't respond to insulin |
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what hormone is produced by the pineal gland?
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melatonin
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what is the precursor molecule to melatonin?
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serotonin (produced from tryptophan)
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name the three zones of the adrenal cortex and the hormones that they secrete.
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1. zona glomerulosa - aldosterone
2. zona fasciculata - cortisol, androgens, estrogens 3. zona reticularis - cortisol, androgens, estrogens |
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what secretes aldosterone?
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The zona glomerulosa of the adrenal cortex
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What secretes cortisol?
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The zona fasciculata and zona glomerulosa of the adrenal cortex
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what is the rate-limiting chemical reaction of the synthesis of corticosteroids?
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cholesterol --> pregnenolone
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what molecule is the precursor to all steroid hormones?
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cholesterol
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what is the main mineralocorticoid?
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aldosterone
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what type of hormone is aldosterone and where is it made? Be specific.
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a mineralocorticoid that is made in the zona glomerulosa of the adrenal cortex
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what enzyme is required in the synthesis of glucocorticoids?
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17-α hydroxylase
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what are the three main groups of hormones produced by the adrenal cortex?
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1. mineralocorticoids
2. glucocorticoids 3. androgens and estrogens |
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the ENZYMES involved in the synthesis of steroid biosynthesis in the adrenal cortex are based on what core molecule?
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cytochrome P-450
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typically, what percentage of cortisol is in its free state?
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5-10%
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what major effects do transport proteins have on steroid hormones?
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- control the bioavailability (equilibrium favors the bound state)
- prolong the half-life (via the above mechanism) - make them more water soluble |
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what organ(s) control(s) how much cortisol is produced by the adrenal cortex, and how is this accomplished?
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1. cortiotropin releasing hormone (CRH) is produced by the hypothalimus and released into the adenohypophysis
2. this stimulates the production and release of ACTH and pro-opiomelanocortin (POMC) into the blood stream 3. these hormones are "cortiotropic" to the adrenal cortex |
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how is the release of glucocorticoids such as cortisol kept in check?
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a long-loop negative feedback mechanism: glucocorticoids inhibit the hypothalamus from secreting CRH
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what five major hormones can be produced from the metabolism of pro-opiomelanocortin (POMC)?
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1. ACTH
2. α-MSH 3. β-endorphin 4. γ-lipotropin (LPH) 5. corticotropin-like intermediate peptide (CLIP) |
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POMC is secreted by which gland?
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(pro-opiomalanocortin)
anterior pituitary gland and pars intermedia of the pituitary gland |
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after POMC is translated from mRNA by ribosomes, it is modified in the Golgi in different ways depending on the gland. Explain the differences.
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(pro-opiomalanocortin)
anterior pituitary: primarily ACTH is produced pars intermedia: dofferent from the anterior pituitary gland in that it is controlled by neural stimulation: - stimulated by β-adrenergic and serotonergic neurons - inhibited by dopaminergic neurons |
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what secretes ACTH and what class of hormone is it?
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the anterior pituitary gland. It is a peptide hormone.
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true or false: secretion of adrenal steroids are controlled by many different POMC-derived tropic hormones? Explain your answer.
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false. ACTH is the only POMC derived hormone that controls secretion of adrenal steroids.
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how does the secretion of CRH vary temporally?
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(corticotropin relasing hormone)
- released in a pulastile manner - in some species, there is diurnal variation. |
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of the hormones secreted by the adrenal cortex, which exists in the highest percentage of the free state in circulation?
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aldosterone
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what tensors on the body stimulate the release of CRH?
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(cortiotropin releasing hormone)
- stress - hypoglycemia - exercise - hypotension - episodic (periodic) release - diurnal in some species |
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what hormones stimulate the secretion of ACTH?
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CRH and vasopressin (ADH)
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what is the basic physiologic process of how steroid hormones act upon and cause a change in its target cell?
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1. diffuse into cell
2. bind to a receptor in the cytoplasm 3. receptor/hormone complex binds to DNA and activates or inhibits gene transcription 4. resultant mRNA is converted to a protein in the ER and processed by the Golgi |
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true or false: glucocorticoids only bind to glucocorticoid receptors and mineralocorticoids only bind to mineralocorticoid recpetors?
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false. although a steroid has the highest affinity to its own receptor, glucocorticoids can bind to mineralocorticoid receptors; however, mineralocorticoids cannot bind to glucocorticoids
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how do glucocorticoids affect carbohydrate metabolism?
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1. increase gluconeogenesis and glycogenolysis in the liver
2. have a permissive effect of epinephrine and glucagon to stimulate gluconeogenesis, glycogenolysis, and lipolysis 3. stimulate production of gluconeogenesis precursors 4. inhibit the action of insulin |
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how do glucocorticoids affect the insulin and glucagon balance in the body?
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"tips the scale" toward glucagon to stimulate the production and release of glucose into the bloodstream
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how do glucocorticoids affect lipid metabolism?
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they have both an indirect and direct affect on lipolysis
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how do glucocorticoids affect protein metabolism?
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enhance proteolysis in most tissues (e.g. skeletal muscle breakdown)
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how do glucocorticoids affect connective tissue?
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inhibit fibroblast activity and collagen synthesis. wounds will heal slower
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how do glucocorticoids affect the CV system?
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1. increase vascular tone
2. enhance myocardial contractility 3. in the heart and BVs, increase the sensitivity to catecholamines |
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how do glucocorticoids affect the immune system
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immunosuppressive
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true or false: glucocorticoids are natural anti-inflammatory compounds?
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true. they help to prevent hyper-inflammatory responses to insult.
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how can glucocorticoids be beneficial when an individual is acutely stressed (e.g. flght or flight)?
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1. enhanced gluconeogenesis, lipolysis, and glycogenolysis boosts blood sugar
2. increased heart contractility and vasoconstriction allows for higher blood pressure to get O2 to those cells. 3. when you are running fron a swarm of bees, the anti-inflammatory effect may help your eyes from swelling shut until you are safe. |
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what are the three main regulators of mineralocorticoid secretion?
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1. plasma K+ concentration
2. renin-angiotensin-aldosterone system 3. ACTH |
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specifically, where is renin secreted?
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by the juxtaglomerular cells of the afferent arteriole in the kidney
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what three major factors stimulate renin release?
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1. decreased blood pressure in the afferent arteriole of the kidney (mediated by prostaglandins)
2. when the macula densa of the renal distal tubule senses low NaCl delivery 3. β-adrenergic stimulation of juxtaglomerular cells (e.g. if you are attacked by a swarm of bot flies) |
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what inhibits renin release from the juxtaglomerular cells of the kidney afferent arterioles?
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1. angiotensin II (a negative-feedback mechanism)
2. ADH (vasopressin) 3. atrial natriuretic factor |
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what is the function of renin?
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cleaves angiotensinigen to angiotensin I
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what is the function of angiotensin converting enzyme, and where is its major location in the body?
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converts angiotensin I --> angiotensin II
in the lung endothelium (and many other tissues) |
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where is aldosterone secreted?
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by the zone glomerulosa of the adrenal cortex
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what stimulates aldosterone secretion?
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1. elevated plasma K+
2. angiotensin II 3. ACTH (minor relative to the other two) |
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what inhibits aldosterone secretion?
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1. low plasma K+
2. atrial natriuretic factor (ANF) |
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where is atrial natriuretic factor produced?
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atrial myocytes
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what stimulates the release of atrial natriuretic factor?
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stretching of the atrium
- fluid retention - congestive heart failure |
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true or false: atrial natriuretic factor and aldosterone work together and have similar effects on the body.
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false. they work in opposition, much like insulin and glucagon.
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what are the 5 major affects of atrial natriuretic factor?
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1. inhibits Na+ reabsorption in the renal collecting duct
2. increases glomerular filtration rate 3. inhibits renin secretion 4. inhibits aldosterone secretion 5. vasodilation |
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what are the major functions of angiotensin II?
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1. stimulates the release of aldosterone
2. arteriolar vasoconstriction 3. stimulates thirst |
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how does atrial natriuretic factor increase glomerular filtration rate (GFR)?
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- dilates renal afferent arteriole
- constricts renal efferent arteriole - these two effects increase glomerular hydrostatic pressure and this increase GFR |
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what are the main functions of aldosterone?
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stimulates Na+-K+-ATPase activity in the renal distal tubule and collectin duct which:
1. conserves sodium 2. excretes potassium 3. stimulates H+ excretion |
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what four general controls does the renin-angiotensin-aldosterone system use to manage homeostasis?
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1. regulates blood volume
2. regulates blood pressure 3. regulates acid-base balance 4. regulates Na+ and K+ balance |
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what two things can be measured to test the activity of the renin-angiotensin-aldosterone system?
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1. renin activity
2. aldosterone concentration |
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why is testing blood plasma cortisol levels an ineffective way to determine adrenocortical function?
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because cortisol concentrations vary widely by a number of factors.
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what tests are used to diagnose hyper- or hypoadrenocorticism?
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1. ACTH response test - adminster ACTH and measure cortisol response
2. dexamethasone suppression test - this supresses CRH and ACTH release and should result in lower cortisol levels unless hyperadrenocorticism is present 3. measure plasma ACTH levels |
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what is the composition of the functional part of the adrenal medulla?
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modified post-ganglionic neurons
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what is secreted by the adrenal medulla?
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catecholamines such as norepenephrine and epenephrine
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what is the amino acid required to synthesize catecholamines?
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tyrosine
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what is the reaction pathway to synthesize epenephrine from tyrosine (not the enzymes, just the products)?
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tyrosine --> DOPA --> dopamine --> norepinephrine --> epinephrine
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true or false: the adrenal medulla is NOT the major source of the catecholamine hormone norepinephrine?
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true. most norepinephrine is derived from leakage of neurotransmitters from sympathetic synapses
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what are the various effects of catecholamine based α1-adrenergic stimulation?
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1. constricts vascular smooth muscle
2. dilates the pupils 3. increased heart contractility 4. constricts the sphincter muslces of the urogenital tract 5. uterine contraction |
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what are the various effects of catecholamine based α2-adrenergic stimulation?
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1. inhibits neurotransmitter release at some adrenergic and cholinergic nreve terminals
2. makes some vascular smooth muscle vasodilate |
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what are the various effects of catecholamine based β1-adrenergic stimulation?
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1. increase heart contractility
2. increase lipolysis in adipocytes 3. increase renin secretion in the kidney |
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what are the various effects of catecholamine based β2-adrenergic stimulation?
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1. vascular smooth muscle dilation, especially in skeletal muscle
2. bronchodilation 3. promotes glycogenolysis and gluconeogenesis in the liver |
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what is the mechanism of action of catecholamine stimulation of β1-adrenergic receptors?
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activate adenylate cyclase (cAMP)
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what is the mechanism of action of catecholamine stimulation of β2-adrenergic receptors?
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activate adenylate cyclase (cAMP)
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what is the mechanism of action of catecholamine stimulation of α1-adrenergic receptors?
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phospholipase cascade --> IP3 --> increased cytosolic Ca2+
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what is the mechanism of action of catecholamine stimulation of α2-adrenergic receptors?
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inhibit adenylate cyclase (no cAMP)
activate K+ channels (membrane depolarization) |
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what two factors can cause an up-regulation of transcription of β-adrenergic receptors?
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- blockage of existing receptors (e.g. with a beta-blocker drug)
- increased thyroid hormone |
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what can cause an down-regulation of transcription of β-adrenergic receptors?
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prolonged elevation of catecholamine levels (almost like a tolerance effect)
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what can cause an up-regulation of transcription of α-adrenergic receptors?
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higher cortisol concentraton
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how does catecholamine release affect the GI system?
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- shunts blood away from the GI tract
- inhibits GI motility - sphincter contraction |
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how do increased α- and β-stimulation respectively affect hormone secretion in the endocrine system?
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α: inhibits hormone secretion
β: stimulates hormone secretion |
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what are the four major chemicals controlling calcium homeostasis?
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1. PTH
2. Vitamin D 3. Calcitonin 4. Phosphorous |
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comment on the distribution of plasma calcium.
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50% is free Ca2+
40% is bound to albumin 10% is complexed with anions such as citrate or phosphate |
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parathyroid hormone is secreted by which cell type?
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chief cells of the parathyroid gland
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what is the primary stimulus for PTH secretion
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hypocalcemia
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what are the two primary inhibitors of PTH secretion?
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1. high calcium levels (a negative feedback mechanism)
2. 1,25-dihydroxycalcitriol |
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what are the four major physiological factors controlling plasma calcium concentration?
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1. GI absorption
2. bone reabsorption 3. urinary loss 4. PTH and Vitamin D levels (also calcitonin) |
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how does PTH affect plasma Ca concentration and how does it achieve this affect?
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1. increase reabsorption by the renal distal tubule
2. Ca bone release 3. increased kidney Ca-Na exchange 4. activates the conversion of Vitamin D to its active form |
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how does 1,25-dihydroxyVitamin D affect plasma calcium levels?
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increased GI absorption
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true or false: Vitamin D is hydrophilic and therefore readily soluble in the blood plasma
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false: requires a carrier protein because it is lipophilic
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by what two means does the body acquire/activate Vitamin D?
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1. UV light in the skin
2. diet |
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basically, how does calcitonin increase calcium levels in the plasma?
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up-regulates the transcription of GI Ca channels and also upregulates the synthesis of Ca binding proteins
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where is calcitonin produced and what does it do?
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produced by the thyroid gland, it acts to inhibit the breakdown of bone by osteoclasts
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how does phosphate concentration control plasma calcium concentration?
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(PTH enhances renal excretion of phosphate.)
lower phosphate --> more Vitamin D activation --> higher calcium levels higher phosphate --> lowers calcium concentration --> lowers activation of Vitamin D --> lowers PTH secretion phosphate and calcium are reciprocal |
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what is eclampsia?
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hypocalcemia around the time of parturition or heavy lactation.
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name the six hormones of the anterior pituitary gland
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GH, ACTH, LH, FSH, TSH, PRL
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what are four common, general characteristics of "all" hormones (after they have been secreted)?
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1. effective at very low concentraions due to signal amplification
2. specific to receptors 3. modulate receptors (e.g. up- or down-regulate receptor transcription) 4. disposed of by the liver and/or kidney |
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name the seven major hypothalamic adenohypophysiotropic hormones
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1. thyrotropin releasing hormone (TRH or TRF)
2. cortiotropin releasing hormone (CRH or CRF) 3. growth hormone releasing hormone (GHRH or GHRF) 4. gonadotrpoin releasing hormone (GnRH or GnRF) 5. prolactin releasing hormone (PRH or PRF) 6. growth hormone inhibiting hormone (GHIH, GHIF, somatostatin) 7. prolactin inhibiting hormone (PIH or PIF) |
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what is the major product of the pars intermedia of the pituitary gland?
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MSH - melanocyte stimulating hormone
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what are the two major disorders of ADH secretion?
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diabetes insipidis - not enough ADH secretion; kidney can't recover water
syndrome of inappropriate ADH secretion (SIADH) - too much ADH; kidney can't excrete water; water intoxication |
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what is the target of TSH
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thyroid follicular cells
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what is the action of FSH?
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females: promote ovarian follicular growth and estrogen production
males: promote spermatogenesis in the semeniferous tubules both sexes: regulation of secretion |
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what is the action of LH?
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females: promote follicular rupture and formation of a corpus luteum, which produces progesterone
males: promotes testosterone production by interstitial cells both sexes: regulation of secretion |
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what are the five major effects of thyroid hormone?
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1. increase BMR
2. promote growth and maturation 3. increase sympathetic activity of the ANS 4. increase thermogenesis 5. promote proliferation of nervous tissue and mylenization of nerves in perinates |
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what are the #1 and #2 most vascularly perfused glands?
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#1: adrenal
#2: thyroid |
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what are the four functional components of the thyroid gland?
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follicular cells, colloid, parafollicular cells (Ca regulation), capillaries
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what is thyroglobulin and what does it do?
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a peptide chain consisting of a large amount of tyrosine units. used as a scaffold to synthesize thyroid hormone
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where is thyrogolbulin made and stored?
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- made in thyroid follicular cells
- stored in the thyroid colloid |
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where is thyroid hormone synthesized
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in the thyroid follicular lumen (colloid) on thyroglobulin
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what are the steps of iodine transport into the follicular lumen of the thyroid
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1. absorption by enterocytes
2. transported to thyroid follicular cells via the blood 3. active transport of iodide into the folicular cell 4. oxidation of iodide to iodine and transport to the follicular lumen 5. iodine binds to tyrosyl residue on thyroglobulin ("organified") |
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what is reverse-T3?
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when the wrong iodine atom is removed from T4. reverse-T3 is useless and is salvaged.
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what are the major affects of melatonin on the immune system?
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1. stimulates production of progenitors to granulocytes and macrophages
2. stimulates the production of NK and CD4+ cells 3. inhibits the production of CD8+ cells 4. enhances the production and release of cytokines from NK and Th cells |
